Seems to be a calculation/display error. Try setting chips variable to 8 , like --gridseed-options=freq=744,chips=8,per_chip_stats=1 for instance instead of 5. 8 seems to be hardcoded max for some reason and speed is calculated based on that.

Don't quite speak C , but it looks like in https://github.com/girnyau/cgminer-gc3355/blob/master/driver-gridseed.c
info->chips = MAX(0, MIN(8, info->chips));
and
return GRIDSEED_HASH_SPEED * (double)elapsed_ms * (double)(info->freq * info->chips);
are responsible for that.
Number 8 is present in the gridseed version of cgminer as well. No idea why, I found it by mistake the other day when playing with chips variable.